US officials have often said they would meet with Iranian counterparts but that talks would have to be limited to Iraq.

With violence escalating in Iraq, and George Bush, the US president, under increasing domestic pressure to wrap up the four-year-old war, many experts say Tehran could play a major role in stabilising Iraq.

Recently, Bush selected a general as his "war tsar" to oversee the fighting in Iraq and Afghanistan.

The White House tried for weeks to fill the position and approached several candidates who reportedly turned it down, before Lieutenant-General Douglas Lute, the defence department's director of operations, agreed to take the job.